WLAN is a flexible data communication system, usually deployed in so-called hotspots, such as airports and hotels, to provide high-speed data services. People can use wireless terminals, such as mobile phones or laptops, via wireless access, to access the network resources in a WLAN, and the resources on Internet connected with the WLAN.
WWAN is a communication system with broader coverage range, and is deployed to provide voice and low-speed data services. For example, Global System for Mobile Communication (GSM), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA) and Third-Generation Mobile Communication (3G) systems all fall in the category of WWAN.
With development of communication technologies, people put forward more and higher requirements for wireless communication systems. When a WWAN user enters into the area covered by WLAN, the user will hope to enjoy the high-speed data service offered by WLAN. On the other hand, when a WLAN user leaves the WLAN coverage area, he/she may also hope to get support from WWAN services. How to integrate high-speed data transfer of WLAN with the broader coverage range of WWAN, is increasingly becoming a hot R&D issue in wireless communications.
FIG. 1 shows the wireless communication in the network integrating WLAN and WWAN in accordance with the above user requirements. As the figure illustrates, when a MT (mobile terminal) 107 equipped with WLAN interface and WWAN interface is going to access the network resources in Internet, if MT 107 is in a hotspot area covered by WLAN 108, it can access the Internet with high-speed via WLAN interface, through the gateway/AP 106 of WLAN 108 (as the thick dashed line in FIG. 1 shows). If MT 107 is out of WLAN 108 and is not in other WLAN coverage areas, it will handover to use WWAN interface, and access the Internet through base station 105, via gateway 102 in the WWAN (as the thin dashed line in FIG. 1 shows).
Users can enjoy better service provided by the wireless network systems, through handover between WLAN and WWAN interfaces, by adopting the communication mode of FIG. 1. However, referring to the communication in FIG. 1, when MT 107 leaves WLAN 108 and enters into WLAN 109, its WLAN address will change, so a precondition for ensuring the ongoing communication not terminated is how to let the other communicating party know the changed WLAN address. An optional scheme is to upgrade the network systems of WLAN 108 and WLAN 109, so that when the MT enters into a WLAN from another WLAN, the network system of the old WLAN can obtain the MT's new WLAN address from the network system of the new WLAN and forwards the data intended to the old WLAN address to the new WLAN address, and thus the communication can go on. But each WLAN network system has to be modified when this scheme is adopted. For each WLAN network system run by different network operators, this will not only lead to increase of system overhead cost, but also have some difficulty and resistance in practicability.